We've been to the zoo a lot recently. The zebras have been a focus of my oldest son's attention as they went from being "scary" to being his favorite thing to see. I recently explained to him that zebras make the same sound as a donkey.
Yesterday before we left for the zoo, he informed me that "zebras sound like donkeys, they go 'DONK'". I guess I should have explained what a donkey sounds like.